The present invention refers to an electronic delay detonator, protected against electromagnetic oscillations, intrinsically safe and with a time delay precision which would be impossible to be obtained through pyrotechnical charges.
As it is well known by explosive technicians, the delay detonators are commonly used to connect and start explosive charges in rock blasting, mining, tunnel openings, implosions, or controlled blastings.
Fundamentally, the delay detonators must present a predetermined time delay between initiation and consequent detonation of the connected explosive charge. The delay time is introduced to cause a series detonation of the explosive charges, in order to minimize the vibration caused by the blasting, besides propitiating an optimized utilization of energy generated by the explosive, achieving the desired efficiency.
Presently, the most used delay detonators make use, for obtaining delay time, of pyrotechnical columns with varied lengths, containing in its interior a mixture of solids capable of burning at a defined velocity.
In spite of many improvements performed along the years, in search of precise delay compositions, we can notice that the obtained precision is limited when compared to the possible precision obtainable through electronic circuits, which is the state of art technology in the field.
It is worth mentioning that electric sequence devices are used to supply a precise time delay through electric circuits, noting that the connections between the sequence device and the individual detonators are made with electric wires, which causes potential risks to the operator, due to stray currents, or electromagnetic induction caused by high tension lines, broadcast stations, radio transmitters and others. Besides such inconveniences, the electrical wires of the device must be connected to the detonators during all operation, what becomes difficult because of frequent rupture of wires by fragments of blasted material.
It is convenient to mention that the present technology has introduced nonelectric shock wave conducting tubes which eliminate the hazards associated with electric detonators, as it is described in Patent # PI 8104552.
Also known to the blasters is the use of detonating cords with a core of high explosive, connected to elements or blasting caps with pyrotechnical delays, noting that this technological aspect falls upon the aggravating circumstance of typical ground level noise of detonating cords, that contributes to the undesirable vibration level, besides reverting to the unpreciseness of the delay time.
Finally, we have the most advanced technology in the field that introduces electronic circuits in delay detonators.
Concerning the matter, is known the document # PI 8807665, published in Jun. 5th, 1990, that deals with a process to initiate an ignition system with electronically delayed action for explosive charges, in which is mentioned the possibility of energization of the electronic delay system through the melting of a fusible electrolyte, which does not generate electrical current when in the solid state, but it does so in the liquid state. This melting would be obtained by the heat generated by the detonation of an explosive, although the document #PI 8807665 neither presents elucidation concerning the materials that could be used for obtaining said energization, nor gives example of a well succeeded experiment with the utilization of the proposed technique. We come to the conclusion, therefore, that the subject was claimed based in general and vast principles. It is also known the document # PI 9202520, that utilizes a piezoelectrical transductor to transform the pressure generated by an explosion in the surroundings into electrical energy, which is used to activate a digital delay circuit. The electronic delay detonator, the object of the present invention, was secretly idealized and conceived with the purpose of characterizing a technological improvement in the field of safety and precision concerning time delays for detonators. Basically, the proposed detonator combines the intrinsical safety of nonelectrical initiation systems with the precision offered by electronical delay circuits.